Multiple jet carburetor



c. H. BURSON MULTIPLE JET CARBURETOR Oct. 30, 1951 2 SHEETS- SHEET 1 Filed 'Oct'. 14, 1946 BURSON L VZ.,

Oct. 30, 1951 C. H. BURSON MULTIPLE JET CARBURETOR 2 SHEETS-SHEET 2 Filed Oct. 14, 1946 l z//v TDR CHARL H unsoN.

/4 7- 7-7 i? we \/5 Patented Oct. 30, 1951 UNI TED STATES PATENT QFFIiCE MlUL'IFIlLli'v JET CARBURETGR;

Charles H. Burson, Seattle, Wash.

Application Getober 14, 1946, Serial N o. 703,167

Claims.

This invention relates to improvements in. car'- buretors for internal: combustion engines andthe like, having particular reference to. the control of: the mixture under conditionsv of varyingv speed and load.

It is generally recognized that a carburetor having a single fuel. jet will not properly satisfy the varying demands of an. internal combustion engine Working in: a wide range of speeds and power outputs.; A` jet designed to givev a proper air-fuel ratio at low speeds produces too rich a mixture at higher speeds, and a jet` suitable for high speed operation starves the. engine at low speeds. In general it may" be said that a single jet-carburetor'will give theproper mixture at only one speed', the mixture being tooY rich. at higher speeds and too lean at lower speeds. This limi.- tation results from an inherent jet characteristic whereby the fuel dischargeis increased and decreased disproportionally to variations in the velocity of' air flow past the'. jetrin the carburetor venturi.

It has., therefore, become common practiceto provide the carburetorsof internal combustion engines with at l'east two jets in which one jet serves for idling." andi only very low speeds,.and the other jet functions exclusively in the normal operating range of the engine. The use of two jets may provide a correct mixture for idlingv and a correct;` mixture for some particular speed and load condition. in the operating range. but under all other conditions. the engine demands are not properly and, eiiciently satisfied.. Carburetors have also previously been. made. with more than two jets inv an attempt to overcome or campen.- sate forV the inherent-'limitations mentioned. above, but such carburetors have,. for the most part, been complicated and diiiicult to adjust and maintain in proper adjustmentg. and-usually have not operated in practice to maintain an optimum air-fuel ratio or to control the fuel delivery in close conformity with` the engine demands over a wide range of variation in speed and horsepower output. Complicated and. intricate carburetor mechanisms areV objectionable because of the tendency of movingv parts to either Wear or stick fast where they' cannot be keptI lubricated, and because of the tendency of iinepassa-ges and jets to become clogged.

Itis.. therefore, a general object ofthe present invention to provide an. improved carburetor which will closely control the air to fuel ratio in accordance with engine demands under variable. operating conditions.v

Another objectlisto provide a carburetor which will automatically obtain maximum economy from an engine in one. operating range. and maximum power in another' operating range without any changev of adjustment'.

Another object is to provide, an improved'carburetor` construction which is; particularly adapted to internal. combustion engines such as automotive engines having extreme ranges of speed and power requirements Another object is to provide an improved carburetor ofthe type described which is of relatively simple and inexpensive construction, which is rugged and reliable in operation and which may be made entirely automatic itsl mixture control so as to require nov unusual adjustmentsl in use.

In accomplishing the general objects hereinabove stated it is av particular object of the present invention to provide an improved carburetor construction utilizing multiple fuel jets for introducing gasoline into the moving air stream under the control of automatic means tovary the number of active jets in accordance with engine demands under dilerent operating conditions to maintain optimum predetermined air to fuel ratios under all different combinations of speed and load' which maybe encountered in the use of the engine.

A still further Objectis toprovide a variable venturi to include more or fewer activeA jets in the Venturi opening in accordance with the volume of air drawn in by engine suction.

With these and other-objects in View the invention resides in the arrangement of parts and details of construction shown by way' of illustration in certain preferred embodiments on the accompanying drawings and described in the following specication.

Figure 1 is a fragmentary plan view of one embodiment of the present invention with certain parts shown in section on the line I-i of Figure 3;.

Figure 2 is av sectional view taken on the line 2 2 of Figure 1;.

n Figure 3 is a. sectional. view at right angles to Figure 2r taken on. the line 3--3 of Figure 1;

Figure 4 is an enlarged fragmentary view of the fuel allocator shown in Figure 3 with. certain parts shown in section.;

Figure 5f is a cross sectional View of the fuel allocator taken on theline 5 5 of Figure 4.-;

Figure 6 is an enlarged view of a modied form of fuel flow impairment valve having an orifice incorporated in al special insert associated. therewith;

Figure 7 is a cross sectional View of the valve and orifice insert shown in Figure 6;

Figure 8 is a sectional view of the fuel allocator taken on the line 8-8 of Figure 7;

Figure 9 is a sectional View showing a modied form of fuel allocator having a square edge orifice formed n the cap;

Figure l is a sectional view showing a tapered orifice formed in the fuel allocator cap;

Figure 11 is a sectional view showing a square edge orifice in the form of a removable insert in the body of the fuel allocator;

Figure 12 is a sectional View showing a tapered orice in the form of a removable insert in the body of the fuel allocator;

Figure 13 is a fragmentary sectional view taken as Figure 3 showing a modified construction having a non-adjustable fuel allocator;

Figure 14 is a view similar to Figures 3 and 13 showing a further modification having only three jets;

Figure 15 is a sectional view showing a further modification having inverted reeds; and

Figure 16 is a view taken as Figure 1, of a modification especially adapted to utilize the central ports n the fuel allocator as idling ports, to make the use of a throttle edge idling port unnecessary.

In the embodiment shown in Figures l, 2 and 3, the numeral I0 designates a vertical carburetor barrel forming an induction passage to the intake manifold of an internal combustion engine. The barrel I0 has a circular upper end II to communicate with an air filter or other source of air supply for the engine and a lower end having a flange I2 of standard construction for connection with the intake manifold of the engine. The numeral I3 designates a conventional float bowl mounted on or forming a part of the barrel I@ and having the usual iioat I II for maintaining the gasoline or other liquid fuel at the level indicated at I5. Within the float bowl are two or more vents I6 above the liquid level and one or more openings Il slightly below the liquid level as shown, the top of the float bowl being sealed by the cover I3a. In the operation of the engine the liquid fuel in the float bowl passes out of the opening Il and is consumed by the engine, causing the float I4 to drop to admit sufiicient fuel from a fuel supply pipe, not shown, to restore the fuel in the bowl to the level indicated at I5.

The lower part of the barrel ID includes a circular section I3 and a transition and Venturi section I9. A conventional butterfly throttle valve 20 operable by an external crank 2I is pivotally mounted in the section I8. A suitable adjustable stop is provided for the throttle valve so that in the closed position there is sufficient leakage to operate the engine at idling speed. Fuel for operating the engine at idling speed may be obtained from a conventional throttle edge idlingport 22, although, as will be hereinafter pointed out, this port may be entirely eliminated if desired. The port 22 is fed from the opening Il in the carburetor bowl, or from an independent opening similarly located, which connects With the port 22 through passages formed in the walls of the barrel I0 and the carburetor bowl under the control of an idling adjustment screw 22a in the usual manner. When the port 22 is used it operates in a manner understood in the art to supply fuel only when the throttle valve 20 is nearly closed so as to cause a high velocity emulsion of air and fuel to issue around the edge of the valve blade and past the opening of the port. This fuel emulsion is produced by an idling jet, not shown, which is of any conventional type as it forms no part of the present invention. At higher engine speeds when the throttle valve is opened to a more nearly vertical position the suction immediately across the opening of the idling port is reduced so that it then .becomes inactive and ceases to supply fuel.

In the upper end of the barrel I0 is a transition ring 23 having a circular outside shape to nt in the circular part I I, and having a rectangular or square opening 24therein. A pair of flexible reeds 25, made of thin, curved spring material such as stainless steel are mounted and secured as by the screws 26 on opposite sides of the opening 2d in inclined positions so as to restrict the opening through the induction passage. The transition ring 23 has a vertical extension 2l within the barrel I0 of square cross section approximating the size of the opening 24, and adapted to t closely on opposite sides of the reeds 25 with a fairly small clearance. When there is no air flow through the carburetor and the reeds are in relaxed condition they assume the positions indicated in full lines in Figure 3, but their flexibility is such as to allow them to bend backwardly to the broken line position indicated at 25' when a large volume of air is flowing therebetween, and to thereafter flatten out to increase the size of the opening even more at exceptionally high rates of air flow. The reeds thereby form movable side walls of a variable rectangular venturi which is responsive to the volurne 0r rate of air flow.

The ring 23 and vertical extension 21 constitute a cage or holder for the reeds within the induction passage of the barrel I0 whereby they may be easily removed without removing the carburetor barrel from the engine. While the part 2l of the reed cage is shown to be rectangular within, its outside may be either rectangular or circular to fit the shape of the mid section of the barrel i0, but it is preferable to make this part of the barrel also square or rectangular. The reeds and cage 2l may also be of Wedge or hour glass shape as viewed in Figure 2 whereby the cage forms two fixed Venturi walls and the reeds form two variable Venturi walls to produce a variable rectangular Venturi throat section. The ring 23 provides a transition section between the circular barrel end I I and the rectangular venturi, and the xed venturi I9 provides a transition section back to the circular lower end I8. Other purposes and advantages of the venturi I9 will be mentioned hereinafter. The lower ends of the reeds are curved to allow a smooth air flow away from the throat of the venturi.

The lower end of each reed is provided with an elongated opening 28 to surround a similarly shaped fuel allocator 3U extending transversely across the induction passage at right angles to the reeds. The fuel allocator is relatively thin and shaped to oifer a minimum obstruction to the flow of air through the carburetor. Its top and bottom edges are curved as indicated at 3l and 32, to conform to the sweep of the reed openings while at the same time maintaining a fairly small clearance therewithin. The curved edges 3| and 32 are substantially parallel whereby the fuel allocator has a uniform height throughout its length so that it can be inserted and removed through openings 33 in one side of the barrel and reed holder. A tapped hole 34 in one end of the body of the fuel allocator provides attachment for a handle piece for removal of the fuel allocator.

When the fuel allocator 30' is inserted through the hole 33 the leading end is received in. a similar hole 35 in an. opposite wall of the extension 2l and seated against the inner wall of the barrel i-, in which position it may be held by a screw 36 and byother parts which will now be described. When the fuel allocator is thus assembled in the barrel, a horizontal gallery passage 3l registers with a fuel passage 38 which is connected with the opening Il in the carburetor bowl, a gasketI 33 being provided toV seal the joint betweenA the parts. A drain plug 38a is provided to drain the passage 38 if desired when the allocator is removed. A plurality of vertical fuel passages d!) rise from thegallery'passage 3l` at intervals alone the: length of theY fuel allocator'and communicate with jets hereinafter described and pairs of discharge ports 4I exposed on opposite side surfaces of the allocator and symmetrically disposed on opposite sides of the central or restposition of the reeds. The vertical position of the fuel allocator 3U withy respect to` thecarburetor bowl is such that the quiescent liquid level stands in an intermediate positionv in the riser passages MI above the level of the gallery passagek 3l and b'elow the level of the discharge ports 4l when the air pressures in the induction passage and carburetor bowl are equalized. Vents t2 behind the reeds communicatev with the openings i6 in the carburetor bowl to maintain this equilibrium cf pressure at all times for those` of the ports di which are disposed behind the reeds, and for all of the portswhen there isinoY substantial air flow passingr through the carburetor to produce a de'- pression between the reeds. Thus, fuel. will issue only from those ports whichv arev exposed'toV pressures depressed below the pressure existingv on top of the liquid in. the carburetor bowl: as determined by the. positions of the reedsl relative to the ports.

Extending through the vertical fuel passages MI a fuel flow impairment valve d5. which may be adjusted by an external lever 46. This valve comprisesv a rotatable shaft or rod extending through al sleeve i8' which may be' screwed into the body of the fuel allocator when the latter is installed in the. barrel la. A pair: of nuts'lffhold the parts in place to provide a rigidbearing for rotation of the valve shaft and leverand. permit the sleeve to be unscrew'ed` when the fuel allocator is; to be removed, whereby the sleeve assists the screw 3S' in securing: the allocator rigidly in the barrel. This valve is preferably located above the quiescent fuel level in the passagestfso as to obviate the necessity for packing te preventleak.-

agel when the carburetor is not operation. When the carburetor is operating. the'impairment lvalve is either at or below atmospheric pressure so there can be no leakage.

The fuel flow impairment valve: l5l provides a means for adjusting the relative discharge rates of fuel through. the Variousy discharge ports 4l in order to best satisfy thev varying demands of an internal combustion engine under different operating condi-tions.` Thisl is accomplished by forming valveV sections on the valve shaft 415 hav'- ing different orice characteristics and indexed to different. relative angular positions to@ effect different. valve openings in the various. passages Hl which supply the ports M. Non-adjustable mreans will also be described for thisY purpose employing jet orifices in the passagesY 40 having different discharge coeicientsV to modify the. dis,- charge.` into ports: 4!- in. response. to chan-ges in the effectivefuel head underl dfiiierentv operating conditions. While the adjustment provided by the valve 45 does not need to be changed in the ordinary operation of the carburetor it is useful toy raise or lower the mixture curve and is of value in engine operation at changing altitudes or with various grades of fuel.

Referring now to Figures 4 to 8, the fuel allocator and two forms of fuel ow impairment valve are shown on an enlarged scale. For convenience in manufacture, and for other reasons the fuel allocator is preferably made in two parts, the body .'i being a permanent member and having an upper part or cap 50 secure thereto by means of screws 5i and containing horizontal bores which form the discharge ports 4I, and vertical bores communicating with the upper ends of the vertical fuel passages lli). As shown in Figures 4 and 5, the valve 45 may comprise simply a cylindrical red passing through the vertical fuel passages di? and having a diameter equal to the diameter of these passages. 'l'h-errod is of cylindrical cross section between these passages and is ground off or relieved as shown at 55 in certain passages to partially open the passage and exert a restrictive action on the fuel flow therethrough in accordance with the angular position of the rod. rih-ezfcontour of each relievedpcrtion 515 is such as to allow a smooth passage of the fuel, the discharge characteristic being that of a rounded orifice. The conditions necessary to obtain this characteristic are a smooth, rounded curvature of the part 55 to minimize cross iiow, and a riser section in the passageV 4D comparable with the valve dimensions. There should be no abrupt changes in the' riser section and it should. be of ample capacity1 to minimize any square edge orifice effects at the junction of the: riser passages ill and the supply gallery 3l. The relieved portions 55 may be` formed entirely on one side of the shaft, as shown, or on opposite: sides' to produceY a more symmetrical flow in the upper end of the riser passage.

Figures 6, 7 and 8 illustrate a form of fuel flow impairment valve having squarev edge orifice characteristics. In this case the rod d5 is ground off to present a fiat side 55a in each of the riser passages and each of these passages is provided` with an'insert cl'osely fitting the rod 45. Each insert 5E is provided with, an opening 5'! in the form of a slit disposed at right angles to the axis of the valve rod whereby the slit is graduallyv uncovered by the flat side 55a as the rod is rotated. Since the surface 55a extends at right angles to the direction of the slit, the area of. thew slit opening varies as a linear functionV of the angular; movement of the valve rod, thereby enabling a precise indexing of the valve action in the several fuel passages and an accurate calibration of the valve in order to obtain a de-` sire'd setting thereof. 'Thel condition. necessary to obtain a square edge discharge characteristic is that the section of theV riser passagey should be large in comparison to1 the discharge slit area, the ratio preferably being lat least four tov one to obtain appreciable side flow.

As will be hereinafter pointed out,.it is intended to employ round orifice valves as shown'in Figure 5in certain of the riser passages, and square: edge orifice valves shown in Figure 7 in other of the riser passages,r but it is within the scope of the invention to make all the valves on shaft of the same but indexed to different angular posi-tions.y

Figures 9 to 12 illustrate different forms of non-adjustable fuel allocator having4 various types of fixedorices in lieu of the adjustable fuel ow impairment valve 45. In Figure 9 the cap 50 has transverse passages `6|] drilled therein to form the pairs of discharge ports 4|, as in the preceding illustrations. Vertical bores 6| connect each passage 6 with one of the Vertical fuel passages 40 and the body 3D. In this case the bores 6| comprise the jets and are smaller than the riser passages 4S to form square edge orifices at 62 on the bottom surface of the cap member.

In Figure I the Vertical bore 6| is enlarged at its lower end in a gradual taper 83 forming a round edge type orifice between the riser 40 and the upper part of the bore 6 In Fig-ures 1l and 1'2 removable and interchangeable inserts are employed to form either round or square edge orices, as desired, in the different fuel passages. sage 40 is enlarged for some distance at 64 to receive either the insert 65 shown in Figure 11 or the insert 61 shown in Figure 12, and the cap member is of less height. The insert 65 has a square edge orifice 66 interposed between the vertical passage 40 andthe bore 6|, and the insert 61 has a round edge or tapered orifice 68 which maintains streamlined flow as the cross sectional area is reduced from that of the Vertical passage 40 to that of the upper body of the insert. The length of enlarged portions 64 allows jet inserts of different lenth to diameter ratios, as well as different tapers to be used.

Fig-ure 13 illustrates a fuel allocator having seven non-adjustable jets of different characteristics. The body is formed with a gall-ery passage 31 and a plurality of vertical riser passages 40 to be supplied from a fuel passage 38 as in Figure 3. The cap 1| is formed with vertical fuel passages communicating with the risers 40. and horizontal passages forming discharge ports at their opposite ends as in the previous embodiment. In this case the central vertical passage in the cap 1| is tapered to form a round edge or tapered orifice 12, and the two adjacent vertical passages on either side are shouldered to form square edge orifices 13. The two end passages 14 have the same size bore in the cap 1| as in the body 10 to promote a large unimpaired flow of fuel when these j-ets are brought into action. At low engine speeds the reeds include in the rectangular Venturi opening only the central jet having the round orifice 12. At higher speeds and loads the square edge orifice jets are included, and finally, under conditions of maximum air flow, the reeds 25 spread apart sufficiently to include and render active the end jets 14. The reason for these different types of jets in this particular arrangement will be discussed hereinafter in connection with the operation of the device.

In Figure 14 is illustrated a modification having three non-adjustable jets. In this construction the fuel allocator 80 has a gallery passage 31 communicating with three riser passages 4! leading to three pairs of ports 4 I. The two outer vertical passages in the cap 8| may be shouldered to form square edge orifices 13 of the type employed on the four intermediate jets in Figure 13, and the central vertical passage may be internally tapered to form a rounded orifice 12. In Figure 14 all three of the jets 12 and 13 are made active when the reeds 25 are spread to the position shown in full lines under conditions of high speed and load. In light running, or cruising, and in idling, only the central jet 12 is in operation, the reeds closing up to the posi- Thus the vertical pas-V tion shown at 25"'in idling. Thus the two outside jets 13 may be termed power jets, an important feature of the invention being that these power jets are activated automatically by reed deflection according to the engine demands, instead of by a mechanical action connected with the throttle as has been a conventional mode of control of power jets in the prior art.

Figure 15 illustrates a modified construction in which the reeds are inverted. The vertical downdraft carburetor barrel 84 here contains a non-adjustable fuel allocator 85 having a cap 86 with a plurality of ports 4|. This allocator may be of the type shown in Figures 13 or 14, or it may be of the variable type illustrated in Figures 4 to 8. Surrounding the fuel allocator and fitting closely within the barrel 84 is a reed cage or holder 81 having a lower end portion 88 designed to form a transition section in which are mounted the upwardly directed scoop-line reeds 90. The reeds are illustrated in an intermediate position corresponding to a medium power output, from which position they are movable in both directions to increase or decrease the number of discharge ports 4| included in the variable Venturi opening. At idling speeds the reeds assume a position close together on opposite sides of the central ports. and at high speeds the reeds are pushed apart by the inrushing air to include all of the ports 4| therebetween. In order to accommodate the extreme movements of the upper ends of the reeds the barrel 84 is iiared on opposite sides at 9| to receive the tips of the reeds so that the end ports may be uncovered. The barrel may be made in two pieces to facilitate the shaping thereof.

The upper end of the barrel 84 is circular and a transition section may be provided if desired between this circular end and the variable rectangular opening between the reeds. At the lower end of the reeds the end portion 88 of the cage forms a transition section from the rectangular Venturi opening back to the circular shape of the lower end of the barrel. Above the end portion 88 the cage 81 has a square or rectangular inner opening with parallel side walls lying closely adjacent the edges of the reeds so that all the air passing through the carburetor barrel is thereby forced between the reeds. The cage and reeds may be of hour glass shape, viewed at right angles to Figure 15, as previously mentioned'in connection with Figure 2, to centralize the air flow around the central ports at idling and low running speeds. The central ports may then serve as idling ports in lieu of the usual throttle edge idling port. The upper ends of the reeds are curved outwardly so that they will be forced apart in the manner described by the inrushing air. In this arrangement the carburetor float bowl |3 is vented to atmosphere as the spaces behind the reeds are at substantially atmospheric pressure.

The arrangement shown in Figure 16 may be utilized to increase the velocity of air flow over the central ports 4| in the fuel allocator 30 at idling speeds so that the throttle edge idling port 22 may be eliminated. Here the reeds 95 are formed and mounted to spring together at 98 to completely close the Venturi throat except for a small opening 96 to include the central ports. The size of this opening is determined by deformed portions 91 in the reeds which eX- tend only slightly on either side of the fuel a1- locator to centralize the air ow when the reeds are closed together as shown. A sufficient ldepression is thereby produced in the opening 96 to activate the central ports at idling speeds. If desired, the central ports may be placed in a lower position closer to the ouiescent fuel level in the riser passages in the construction of Figure 16 and also in the vother embodiments to provide adequate discharge at :the idling depression. At higher speeds and loads the reeds are deflected apart by the inrushing air as in the case of reeds 255 to increase the Venturi opening and the number of Venturi ports in accordance with the engine demands. The deformed por.- tions 97 `need .extend only for a short dis-tance along the reeds where `their curvature brings them `close together above and below the line of ,contact rat 98. This form of reed may be used in any of the different embodiments hereinabove described. If employed ,in Figure it would have the advantageous effect .of reducing the spread of the reeds to `uncover all :the discharge ports, so that the flares 9| in the barrel would be unnecessary.

Operation In .the different ,embodiments it will be apparent that the two flexible vreeds are .deflected by the inrushing .air -so as to .be separated to form .a variable rectangular venturi in accordance Vwith the demands ofthe engine., the reeds automatically changing the size cfthefopening therebetween according ,to .the volume of Aair which is required by the suction displacement of the engine. The vmovemr-:nt l.of .the reeds uncovers and .brings into action additional vfuel jets as required Yto `maintain the desired air fuel mixture ratio for larger volumes .of air withont depending entirely upon increased iiow from the iets which are rlirst :in operation. The ldischarge capacities v.and/ or coeiicients of .the active iets thereby modify the mixture ratio for different engine demands whereby the mixture ratio may be caused to vary according to a predeterminedcurue to :meet the particular needs @.f .dierent operating conditions of an internal Combustion engine.

The reeds l,and the two slides .of the holder comprise a 4rectangular air conduit `of variable net cross sectional :area in the Venturi throat., which area -a function of the reeds .deflection from a central, normal or rest position. The designof the `parts is such that ,themaximum net area .occurring when `the reeds .are .fully deflected .provides sufficient capacity `to `accommodate -the engines greatest air demands. In all embodiments the pairs -of discharge ports di are `symmetrically disposed with respect :to the 4 central or rest position of the breeds, `and the por-ts are designed to give a symmetrical and quadrantal fuel discharge, That is to say that the discharge is symmetrical and equal in all four 4quadrants-of the cross sectional area of the Y Venturi throat -for all positions ,of the reeds. The jets ,may be of any type. .Some .orrall of them may be .of the submerged type and the jets and Ydischarge ports may be mounted from the carburetor bowl or reed cage, i-f desired, rather than in a transversely extending fuel allocator, although the latter arrangement is utilized Ain .the ,present embodiments to illustrate the operating principles of the invention.

When an :internal-.combustion engine is in oper.- a-tion with the present .carburetor `in any 4of its various forms,` .the reeds arel deflected in the manner described .by the inrushing air, their dejets are included in the` Venturi flow to ,supplyv an increasing quantity of fuel to the greater quantity of air. The flow of air through the induction passage and between the reeds is pro` duced by a pressure gradient established by the suction ,of the engine whereby the pressure in the intake manifold lis depressed below atmospheric pressure. The action of the air flow between the reeds produces local variations in pressure in .Ciiierent parts of the carburetor which are utilized to bring additional jets into action in accordance with the principles of the invention. The Vjets behind the reeds are maintained inac tive by equalizin-g the pressure behind the reeds and the pressure on the surface of the fue] in the carburetor bowl through the communicating ports IB and e2. Fuel in the riser passages 40 behind the reeds is therefore exposed to the same pressure through the ports 4I as the fuel in ,the carburetor float bowl whereby the fuel in these passages is maintained at the float bowl level and does not issue through ports 4l. The ports in the Venturi opening between the reeds however are exposed to a lower pressure by rea.- son of the air velocity, causing fuel to discharge therefrom. The parts are designed so that the differential depression thus created is always in excess of the minimum head necessary to discharge the fuel. This minimum head consists of that `head necessary to overcome the surface tene sion of the fuel plus the vertical height from the quiescent fuel level to the port openings 4| The fuel which is discharged into the high velocity air stream between the reeds is atomized and carried on to the engine induction system. In passing the transition and Venturi section I9 the atom ized fuel becomes more thoroughly distributed and mixed in the flowing air stream. The diierential or Velocity depression causing fuel flow from the active ports is controlled by the dimensions of the air intake conduit system .comprising the reeds and holder sides, and the stiffness of the reeds.

There is an Aadvantage in large jet and port areas in that the possibility of the passages and openings becoming obstructed with foreign matter is greatly reduced. By a suitable selection of air flow areas and reed stiffness the differential depression may be made just sufficient to flow the fuel through the jets at the desired discharge coefficient, while at the same time a major portion of the velocity potential in the air intake stream can be exploited. The effectiveness of fuel atomization in fine particles appears to be a function of the square of the relative velocity of theair with respect to the fuel.

It is apparent that by suitable arrangement of jets of various sizes and characteristics in the fuel allocator any air fuel mixture for any engine range can be obtained. For automotive use a mixture ratio of about 12 to 1 is desirable for lowy speed operation at near idling speeds. At part throttle conditions in the normal or cruising range, economy is desirable and mixtures of 15 to 1 are preferred. From about three-quarter to full throttle a mixture ratio of about l2 to 1 is necessary for providing maximum power. An air fuel mixture curve of this type may be effected by appropriate selection of jet discharge area, jet type, and port placement in thefuel allocator with respect to reed deflection increment.

The shape of the air fuel mixture .curve may be controlled in the adjustable fuel allocator by the relative indexing of the different valve portions on the valve rod 45 in the several vertical fuel passages, and by the use of round edge orice valves in certain risers and square edge oririce valves in other risers, as illustrated in Figures and 7. In the non-adjustable fuel allocator the shape of the mixture curve may be controlled by the use of different sizes and types of orifices in the different jets as illustrated, for example, in Figures 9 to 13. Round edge orices have a relatively linear discharge curve and flat or plate type orifices have a flattened discharge curve, with reference to discharged quantities plotted against head in inches of water. For low engine loads and idling it may be desirable, though not necessary, to have a separate low-load and idling carburetor port such as the port 22 in Figure 3 which is preferably operative up to approximately 450 R. P. M. in the case of automotive engines. At this speed it is preferred that the central jet of the main jet assembly in the fuel allocator gradually commence to discharge. It is also deu sirable that this transition point be passed with smoothness and without abrupt change in mixture ratio. Since the central jet supplies the fuel for light to moderate loads, its characteristic should be somewhat linear. This may be accomplished in the non-adjustable allocator by using a rounded orice such as shown at I2 in Figure 13 or either of the types shown in Figures 10 and 12. In the adjustable allocator, Figure 5 may be considered as illustrating the central jet.

When the load, and consequently air volume, increases to the point where the discharge of the central jet becomes insuincient the diverging reeds bring additional jets into action. It is desirable then that the initiation of discharge from the additional jets be slightly more abrupt than the central jet, and also that they have flatter characteristic curves at higher loads. These additional jets should become effective when the central jet is at or near maximum discharge, and provide a lean mixture through their range, their discharge supplementing that of the central jet. A number of these jets activated in steps is desirable t0 include a wide range of speeds.

At high engine loadings the final or power jets at the ends of the fuel allocator become active. Their discharge characteristics should also be somewhat linear and add to the aggregate jet discharge sufcient fuel to provide a mixture of maximum power.

In a symmetrical arrangement of seven jets the preferred embodiment is to employ round orifice characteristics in the central and end jets, and square edge orifice characteristics in the four jets intermediate therebetween. Thus, referring to Figure 13 as an example, the central pair of ports are served by the round edge orifice I24 and the end pairs of ports are fed by the vertical passages 14 which also have round edge orifice characteristics. The other four pairs of ports intermediate between the central and end pairs are fed through the four square edge orifices 13. The same mixture curve may, of course, be obtained by use of the jet and orifice types shown in Figures 5, '7, and 9 to 12 as hereinabove explained.

Other jet and orifice arrangements may be used, but a primary advantage of the invention is that it is possible by the proper selection of jet characteristics in the individual riser pasl2 sages to produce a mixture of maximum economy or power at any predetermined value or values of engine loading.

The fineness of mixture control is dependent on the number of jets available for progressive activation in the fuel allocator system. With seven or more jets, extremely close regulation of the mixture curve is possible. A fewer number of jets may be used, however, as illustrated in Figure 14 where there are three jets. In this arrangement, the central jet supplies, or meters, suiiicient fuel for light loads and economical cruising ranges corresponding to partial throttle openings. With wide open throttle conditions the remaining two jets are activated, their discharge supplementing that of the central jet and providing a mixture of maximum power, whereby the two outside jets may be termed power jets. The reeds are shown in full lines in positions to produce full discharge from all the jets, and in broken lines in a low speed position.

As has been previously stated, it is not necessary that the different jets all be at the same level with respect to the quiescent fuel level in the Vertical risers 40. If the idling jet 22 is dispensed with, its function may be accomplished by a central jet or jets in the fuel allocator, particularly if these jets are located relatively close to the quiescent fuel level, as mentioned in connection with Figure 16. It may then be desirable to place the port openings 4l at different heights, and possibly to employ the port openings themselves as jets.

The present variable venturi has a beneficial corrective effect upon an undesirable condition in many conventional carburetors known as throttle bias. At partial openings of the usual butterfly throttle valve, particularly in the region of 45 of angular rotation with respect to the carburetor barrel, the quantity and velocity of the flowing medium passing the throttle plate edge on one side is considerably greater than that passing on the other side. The angular position of the throttle plate tends to concentrate the medium on one side and to rarify it on the other side by producing in effect a Venturi orice in one side of the pipe or barrel, and a reentrant orifice in the other side which deects and straties the fuel in the incoming mixture against one side of the manifold producing nonhomogeneity of the mixture finally reaching the engine cylinders. At certain speeds there is a tendency in conventional carburetors as a result of this condition for some cylinders to receive too lean a mixture while others receive too rich a mixture, a condition which has been difficult to remedy without complicating the construction of the throttle valve.

'I'he restricted Venturi passage between the reeds acting in conjunction with the transition and Venturi section I9 tends to centralize and focus the ow of mixture in the center of the carburetor barrel as it approaches the throttle valve, thereby making for a more equitable distribution of the mixture on both sides of the throttle plate. Or, looking at the fuel flow from a different View point. the air between the reeds is subject to suction from somewhat of a point source in the Venturi section I9 which promotes mixing and tends to reduce stratification of the mixture immediately approaching the throttle valve.A Thus, further advantage of the present arrangement is the deflection and intermingling of the fuel mixture ahead of the throttle valve and the free symmetrical flow of the mixture attacca due to the absence of projecting jets or other obstructions in the venturi I9. Since there are no obstructions in the venturi I9, it c-an be made with a-smaller net section than conventional venturis, thereby resulting in increased deflecting and'vfocusing and centralizing actions. The venturi 'I9 acts both as a point source of suction for the variable venturi and as a point source of supply for the mixture flowing toward the throttlevalve, tending to reduce separation of the fuel. Although the throttle valve is shown mounted for rotation on an axis parallel with the reeds ilt may be turned at right angles or in any other relative position because of the centering and focusing .of the flow by the venturi I9 in the manner just described.

In order to simplify and clarify the explanation of the principles of the invention no throttle pump or choke have been shown, but it is intended that the present carburetor should vbe supplied with such equipment. A conventional throttle pump may be employed and the usual choking methods may be used for starting. The choke may comprise the usual butterfly valve ahead of, or in the leading end of, the carburetor barrel, referred to the direction of air flow fin the induction system. The action of the choke should be such as to cause 'the entire .jet system to discharge fuel upon full choke. If the choke is automatic it should be arranged so that the choking action will be materially reduced as soon as :sufficient fuel is in the intake manifold for starting.

The various modifications herein illustrated are .intended to operate as down-draft carburetors, but -:the carburetor barrel may, if desired, be turned `'horizontally or even inverted to serve `as an 11p-draft carburetor without sacricing any of the advantages of the invention except the recognized advantages of having a down-draft flow of the fuel mixture into the engine.

vAs has been mentioned hereinabove it is not essential to the invention that the discharge ports be mounted and arranged in a transverse fuel allocator of the specic construction shown. The ports may be mounted in various ways inthe carburetor barrel so as to be activated successively by movements of the reeds.

The reeds have been described as made of flexible material capable of bending to admit the necessary volume of incoming air, but it is apparent that they may be otherwise constructed and still perform the same function.V They may, for instance, take the form of rigid hinged vanes which are biased to close together to a certain minimum Venturi opening, and adapted to spread apart vto uncover additional fuel ports with an increasing volume of air.

Still other changes may be made in the construction and arrangement of parts and in the use of certain features without others, and all such modications within the scope of the appended claims are deemed to be included in the invention.

-I-Iaving now described my invention and in what manner thesame may be used, what I claim as new and desire to protect by Letters Patent is:

1. A carburetor comprising an induction passage, a throttle Valve in said passage, a multiple jet fuel allocator in said passage ahead of said throttle valve, a variable venturi associated with said fuel allocator to expose a number of fuel jets to the air flow through the venturi in proportion to the volume of air flowing through said passage, all of said jets being open and capable of discharging fuel when :exposed to the air ow in said venturi, and a fixed Venturi section inzsaid passage between said throttle valve and said fuel allocator to assist in mixing the .air and fuel and to centralize the mixture flow in ysaid pas sage leaving said fuel allocator .and approaching said throttle valve.

2. In a carburetor, an induction vpassage having an air intake opening at one end and a throttle valve at the other end, a pair `of flexible reeds on opposite vsides of said passage between said intake opening and `said throttle valve, said reeds vhaving free elastic response to air flow throughsaid passage to form a variable venturi, a horizontal fuel allocator extending across said passage between said opposite sides perpendicular to said reeds and in the region swept by the movements of said reeds, and a Aseries lof open fuel discharge ports spaced along said allocator, the central one of said ports ybeing included in the throat of the venturi at all times and the remaining ports being included in variable number as the reeds move apart in response to increasing air flow.

3. In a carburetor, an induction passage having an air intake opening, a throttle valve :spaced from said intake opening, a pail1 of flexible reeds on opposite sides of said passage between said intake opening and said throttle valve, lsaid reeds having free elastic response to air flow through said passage to form a variable ventu-ri, a horizontal fuel allocator extending across said passage between said opposite sides perpendicular -to said reeds and in the region swept by the-movements of said reeds, a series of fuel discharge ,ports spaced at intervals along said allocator, all

of said ports being open at all times, and means for maintaining liquid fuel `in said allocator iat such `level that only those ports exposed tothe reduced pressure in the throat of the variable venturi will discharge fuel -while those ports be' hind said reeds on opposite sides of said'passage will not discharge fuel.

4. vIn a carburetor, vertical induction passage, a

f pair of flexiblereeds on opposite sides of said'passage having 'free elastic response `to air flow through said passage to form a variable venturi in the center of said passage, a horizontal fuel allocator extending across said passage between said opposite sides perpendicular to said reeds in the region swept by the movements of said reeds, a series of open fuel discharge ports spaced along said allocator to be exposed in variable numbers to `air flow through said venturi between said reeds depending upon the positions of said reeds, the remaining ports being shielded from said air flow in spaces behind said reeds at Said opposite sides of the passage, a float bowl connected with said allocator to maintain a predetermined quiescent liquid fuel level in said allocator below the level of said ports, and vent passages connecting said spaces behind the reeds with the .top of said oat bowl to equalize the air pressure in lsaid float bowl with the pressure existing in said spaces for preventing fuel discharge from the ports vin the spaces behind the reeds.

5. In a carburetor, a vertical induction passage having an air intake at its upper end and a throttle valve at its lower end, a fixed Venturi above said throttle valve, ,said passage having an approximately square cross section for a distance above said fixed venturi, an elongated horizontal fuel allocator extending across said passage in said square cross section, fuel ports spaced along said allocator, and a pair of vertical rectangular free reeds extending acrossy said square section transversely to the length of said fuel allocator with openings closely fitting said allocator and biased toward each other to form a variable venturi eX- posing the central one of said ports to a small volume air stream and exposing additional ports on opposite sides of said central port when the reeds are spread apart by a large volume of air fiow.

6. In a carburetor, a vertical induction passage having an air intake at its upper end and a throttle valve at its lower end, a fixed venturi above said throttle valve, said passage having an approximately square cross section for a distance above said fixed venturi, an elongated horizontal fuel allocator extending across said passage in said square cross section, fuel ports spaced -along said allocator, a longitudinal fuel passage in said allocator, individual riser ducts connecting said ports with said fuel passage, round edge type orifice means in certain of said ducts and square edge type orifice means in other of said ducts, and a pair of vertical rectangular free reeds extending across said square section transversely to the length of said fuel allocator and having openings closely fitting said allocator to form a variable venturi exposing the central one of said ports to a small air stream through said variable venturi and exposing additional ports on opposite sides of said central port when the reeds are spread apart by a large volume of air flow.

7. In a carburetor, a vertical induction passage having an air intake at its upper end and a throttle valve at its lower end, a fixed venturi above said throttle valve, said passage having an approximately square cross section for a distance above said fixed venturi, an elongated horizontal fuel allocator extending across said passage in said square cross section, fuel ports spaced along said allocator, a fuel passage extending longitudinally through said allocator, individual riser ducts connecting said ports with said fuel passage, a common rotatable valve rod intersecting all of said ducts, said rod being relieved in rounded contour in certain of said ducts to form round edge orifices and relieved in angular contour in other of said ducts to form square edge orifices, and a pair of vertical rectangular free reeds extending across said square section transversely to the length of said fuel allocator and having openings closely fitting said allocator to form a variable venturi exposing the central one of said ports to a small air stream through said variable venturi and exposing additional ports on opposite sides of said central port when the reeds are spread apart by a large volume of air fiow.

8. In a carburetor, a straight induction passage having a portion with an approximately square cross section, an air intake opening at one end of said passage and a throttle valve at the other end, an elongated horizontal fuel allocator extending across said passage in said square cross section, fuel ports spaced along said allocator, a pair of free reeds on opposite sides of said passage disposed transversely of said fuel allocator and biased toward each other, said reeds having side edges closely fitting the walls of said passage with small clearance and having openings closely fitting said allocator with small clearance to form a variable venturi exposing the central one of said ports to a small air stream and exposing additional ports on opposite' sides of said central port when the reeds are spread apart by a large volume of air flow.

9. In a carburetor, an induction passage having an air intake opening at one end and a throttle valve at the other end, a pair of flexible reeds on opposite sides of said passage between said intake opening and said throttle valve, said reedsl having free elastic response to air flow through said pasisage to form a variable venturi, a horizontal fuel allocator extending across said passage between said opposite sides perpendicular to said reeds and in the region swept by the movements of said reeds, a vseries of open fuel discharge ports spaced along said allocator, the central one of said ports being included in the throat of the venturi at all times and the remaining ports being included in variable number as the reeds move apart in response to increasing air fiow, a longitudinal fuel passage in said allocator, individual riser ducts connecting said ports with said fuel passage, round edge type orifice means in certain of said ducts, and square edge type orifice means in other of said ducts.

10. In a carburetor, an induction passage having an air intake opening at one end and a throttle valve at the other end, a pair of fiexible reeds on opposite sides of said passage between said intake opening and said throttle valve, said reeds having free elastic response to air flow through said passage to form a variable venturi, a horizontal fuel allocator extending across said passage between said opposite sides perpendicular to said reeds and in the region swept by the movements of Said reeds, a series of open fuel discharge ports spaced along said allocator, the central one of said ports being included in the throat of the venturi at all times and the remaining ports being included in variable number as the reeds move apart in response to increasing air ow, a fuel passage extending longitudinally through said allocator, individual riser ducts connecting said ports with said fuel passage, and a common rotatable valve rod intersecting all of said ducts, said rod being relieved in rounded contour in certain of said ducts rto form round edge orifices and relieved in angular contour in other of said ducts to form square edge orifices.

CHARLES H. BURSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,125,067 Coulter Jan. 19, 1915 1,130,950 Williams Mar. 19, 1915 1,222,672 Reichenbach Apr. 17, 1917 1,257,862 Hess et al Feb. 26, 1918 1,360,445 Rollins Nov. 30, 1920 1,753,235 Duff Apr. 8, 1930 1,787,854 Braun Jan. 6, 1931 1,927,091 Hess Sept. 19, 1933 1,945,189 Goodman Jan. 30, 1934 2,052,225 Hartshorn Aug. 25, 1936 2,167,975 Ericson Aug. 1, 1939 OTHER REFERENCES Hydraulics Schoder and Dawson, 1st ed. 1927, page 122. 

